Theresa May’s official visit to Saudi Arabia this week has once again raised the controversial issue of the UK’s intimate ties with the Gulf monarchy. The UK-Saudi alliance has been portrayed by supporters and detractors alike as having been born from mutual self-interest and realism.

However, a degree of emotional sympathy and traditional Foreign Office Arabism cannot be entirely ruled out. The kingdom would not exist if it were not for British support during the fierce fighting of the First World War and the civil war with the Hashemites. British diplomatic recognition and military support allowed Ibn Saud, the founder of modern Saudi Arabia, to finally unify his country in 1932. American and British forces further defended the state when her oilfields were threatened by Saddam Hussein’s forces, then occupying Kuwait, in 1990-1991.

Britain’s extensive military, political and economic ties with Saudi Arabia have undoubtedly brought enormous benefits to both states. London and Riyadh have invested tens of billions in each other’s economies: British exports numbered £6.57 billion in 2015 alone. 30,000 British nationals are currently estimated to be living and working in the state. But relations with Saudi Arabia have also led to much moral soul searching.

Ever since the notorious 1985 Al-Yamamah arms deal between Margaret Thatcher and Prince Bandar (which is reported to have involved false accounting and millions of pounds of bribes), arms exports to the Gulf state have brought an estimated £43 billion to BAE Systems, the pillar of the UK’s defence sector.

It is a Faustian pact that has been as necessary to our interests as it has been corrosive to our values. So uncritical is our support for Saudi Arabia that Boris Johnson was publicly slammed last year by Downing Street when he stated the obvious point that it was engaged in “proxy wars” with Iran across the Middle East.

The uncertain and fragile state of the landscape in the Southern Gulf means that the survival of Saudi Arabia is intertwined with the stability of the region as a whole. We cannot, however, allow this fact to blind us to the reality that Saudi repression has contributed to the tragic situation that we see today. Nor can we allow Brexit to force us to make lucrative deals with repressive dictatorships and autocracies, even as they commit human rights violations and possible war crimes.

On top of its treatment of women and religious minorities, Saudi Arabia has a medieval record on domestic human rights. In 2015, Michael Gove faced significant pressure when he, in his position as Justice Secretary, rightly cancelled the Ministry of Justice’s bid for a £5.9 million prisons contract after a pro-democracy blogger was publicly flogged and an anti-government activist was sentenced to death by crucifixion.

Although Saudi Arabia has emphasised its commitment to the war on terror and the security of her Western allies, Salafi-Jihadist inspired terrorism has undoubtedly drawn inspiration from the Wahhabist ideology of Saudi Arabia’s clerical establishment as well as its funding of mosques and madrassas across the world.

To date, Saudi nationals comprise the largest group of foreign fighters in ISIS. Saudi Arabia is also widely suspected of having funded jihadist groups in Syria, such as Jabhat Fateh al-Sham (formerly known as the al-Qaeda affiliate Jabhat al-Nusra).

Despite the unfolding humanitarian crisis in Yemen which has claimed an estimated 10,000 lives, half of which are civilians, £3.3 billion of arms has been sold to the Saudi military in its war with the Iranian backed Houthi rebels. The Saudi led blockade has led to starvation, malnutrition and poor medical supplies.

Theresa May has told the BBC that the UK government is “concerned” by the situation and has donated £103 million in humanitarian aid to the Yemeni population. This will be of little comfort to the victims, considering the enormous scale of British investments in the Saudi military thus far. British-made cluster bombs and Typhoon fighter jets have had a particularly devastating effect on civilian populations and are in contravention of our obligations under international law.

This is why raising “hard issues” with Saudi counterparts is not sufficient. Real engagement needs to consider meaningful action. Late last year, two parliamentary committees – the Committee on Arms Export Controls and the Committee on International Development and Business – published a joint report pressuring the British government to stop licensing arms exports to Saudi Arabia. It is absolutely appropriate that a case of judicial review brought against the British Government has been given just consideration by the High Court this February.

Theresa May, if she so chooses, has a renewed opportunity to raise the question of arms restrictions or temporary sanctions against Saudi Arabia with the new Trump administration. US cooperation will be important in holding Saudi military actions to account. Although current US overtures towards Saudi Arabia make such efforts unlikely, the UK can make bold first steps. This scenario marks a real test of an independent and principled post-Brexit British foreign policy. It is also a test that I fear we will fail spectacularly.

The argument that our defence industry relies on Saudi buyers no longer stands up to scrutiny. While we must engage with Saudi Arabia as our ally against terrorism and Iranian expansionism, we must be candid about some of its activities at home and abroad. And we must act accordingly.